GIL Checkbook

To demonstrate GIL's scrolling list capability, we will construct a GIL
application which displays checks in a scrolling list. The user may add checks
to the list, edit checks in the list, and delete checks from the list. A check
has three data items:

number, between 100 and 500 (inclusive)

payee, a text field of up to 30 characters, and

amount, an integer between 1 and 1000. The amount will interpreted
as the number of cents the check is worth - ie a check with amount=300 is worth
$3.00.